Iron(II) sulfate (British English: iron(II) sulphate) or ferrous sulfate are salts with the formula FeSO₄xH₂O. These compounds exist most commonly as the heptahydrate (x = 7) but are known for several values of x. The hydrated form is used medically to treat iron deficiency, and also for industrial applications. Known since ancient times as copperas and as green vitriol, the blue-green heptahydrate is the most common form of this material. All iron sulfates dissolve in water to give the same aquo complex [Fe(H₂O)₆], which has octahedral molecular geometry and is paramagnetic.